The present invention relates generally to a variable temperature seat and, more specifically, to a method and apparatus for controlling the flow and temperature of a heating or cooling medium through the seat to an occupant positioned in such seat.
Cooling or heating occupants of buildings, homes, automobiles and the like is generally carried out by convection through modifying the temperature of air surrounding the occupants environment. The effectiveness of convection heating or cooling is largely dependent on the ability of the temperature conditioned air to contact and surround all portions of the occupants""s body. Heating and cooling occupants through convention is generally thought to be efficient in such applications as homes, offices, and other like structures where the occupants are not stationary or fixed in one position but, rather are moving around allowing maximum contact with the temperature treated air.
In other applications such as automobiles, planes, buses and the like, the occupants are typically fixed in one position with a large portion of their body""s surface against the surface of a seat, isolated from effects of the temperature conditioned air. In such applications the use of distributing temperature conditioned air into the cabin of the vehicle to heat or cool the occupant is less effective due to the somewhat limited surface area of contact with the occupant""s body. In addition, oftentimes the surface of the seat is at a temperature close to the ambient temperature upon initial contact by the occupant, increasing the need to provide rapid temperature compensation to the occupant in an effective manner.
To address the problem of providing effective occupant heating or cooling in such applications, seats have been constructed to accommodate the internal flow of a heating or cooling medium and to distribute the same through the seating surface to the surface of the occupant in contact with the seat. A preferred heating and cooling medium is air. A seat constructed in this manner increases the efficiency of heating or cooling a passenger by convection by distributing temperature conditioned air directly to the surface the occupant generally isolated from contact with temperature conditioned air that is distributed throughout the cabin of the vehicle.
U.S. Pat. No. 4,923,248 issued to Feher discloses a seat pad and backrest comprising an internal plenum for distributing temperature conditioned air from a Peltier thermoelectric module through the surface of the seat pad and to an adjacent surface of an occupant. The temperature conditioned air is provided by using a fan to blow ambient air over the fins of a Peltier module. The heating or cooling of the occupant is achieved by changing the polarity of the electricity that powers the Peltier module.
U.S. Pat. No. 5,002,336 issued to Feher discloses a joined seat and backrest construction comprising an internal plenum for receiving and distributing temperature conditioned air through the seat and to an adjacent surface of an occupant. Like U.S. Pat. No. 4,923,248, the temperature conditioned air is provided by a Peltier thermoelectric module and distributed through the internal plenum by an electric fan.
U.S. Pat. No. 5,117,638 issued to Feher discloses a selectively cooled or heated seat construction and apparatus for providing temperature conditioned air. The seat construction comprising, an internal plenum, a plastic mash layer, a metal mesh layer, and perforated outer layer. The apparatus for providing the temperature conditioned air is heat exchanger comprising a Peltier thermoelectric module and a fan. Heating or cooling the occupant is achieved by switching the polarity of the electricity powering the Peltier module.
The seat constructions known in the art, although addressing the need to provide a more efficient method of heating or cooling the occupant, has not addressed the need to provide temperature conditioned air to an occupant in a manner that both maximizes occupant comfort and maximizes power efficiency.
The ever increasing awareness of our environment and the need to conserve resources has driven the need to replace hydrocarbon powered vehicles, such as the automobile, with vehicles that are powered by an environmentally friendly power sources such as electricity. The replacement of current hydrocarbon automobiles with electric powered vehicles will only become a reality if the electric powered vehicle can be operated and maintained in a manner equaling or bettering that of the hydrocarbon powered automobile it replaces. Accordingly, the need for electric vehicles to perform in an electrically efficient manner, is important to the success of the electric vehicle.
In order to maximize the electrical efficiency of the electric powered vehicle it is necessary that the electrically powered ancillary components of the electric vehicle function at maximum electrical efficiency. The seats known in the art that provide temperature conditioned air to an occupant do not operate in an electrically efficient manner. The temperature of the air being conditioned by the Peltier thermoelectric devices in such seats is adjusted by dissipating the excess power through a resister, i.e., by using a potentiometer. The practice of dissipating excess power instead of providing only that amount of power necessary to operate the Peltier thermoelectric devices makes such seats unsuited for such power sensitive applications as the electric vehicle as well as other applications where electrical efficiency is a concern.
The seats known in the art constructed to provided temperature conditioned air to an occupant are adjustable in that the occupant may either choose to produce heated air or cooled air. However, the seats known in the art are unable to automatically regulate the temperature or flow rate of the cool or heated air distributed to the occupant in the event that the thermoelectric device malfunctions or in the event that the user falls asleep. An electrical malfunctioning of the thermoelectric device could result in the abnormal heating of the device, causing damage to the thermoelectric device itself. An electrical malfunction could result in the distribution of hot air to the occupant, causing discomfort or even injury. Additionally, an initial temperature setting of maximum heat or maximum cold that is left untouched in the event the occupant falls asleep may cause damage to the thermoelectric device itself or may cause discomfort or even injury to the occupant.
The seats known in the art, while able to vary the distribution of air to the seat bottom or seat back via occupant adjustment, do not allow the occupant to vary the temperature of the air passing through the seat back or seat bottom, independently. The option of being able to selectively heat one portion of the seat and cool the other may be desirable where the occupant requires such selective treatment due to a particular medical condition or injury. For example, one a cold day it would be desirable to distribute heated air to the seat back for occupant comfort and cooled air to the seat bottom to assist in healing a leg injury that has recently occurred.
It is, therefore, desirable that a variable temperature seat comprise a control system and method for regulating the temperature and flow rate of temperature conditioned air to an occupant sitting in the seat. It is desirable that the control system operate the seat in an electrically efficient manner, making it ideal for use in power sensitive applications such as the electric powered vehicle. It is desirable that the control system operate the seat in a manner eliminating the possibility of equipment damage, occupant discomfort or injury. It is also desirable that the control system permit the independent distribution of heated or cooled air to the seat back or seat bottom.
There is, therefore, provided in practice of this invention a temperature climate control system for use with a variable temperature seat. The temperature climate control system comprises a variable temperature seat suitable for distributing temperature conditioned air to a seated occupant, at least one heat pump for temperature conditioning ambient air and passing the air to the seat, a temperature sensor located at each heat pump, and a controller configured to monitor the temperature of the heat pumps and regulate their operation according to a temperature climate control algorithm.
Each heat pump comprises a number of Peltier thermoelectric modules for selectively heating or cooling ambient air in a main heat exchanger. The heated or cooled air is passed to the seat by a main exchanger fan. Each heat pump also comprises a waste heat exchanger for removing unwanted heat or cooling from the Peltier modules. The unwanted heat or cooling is passed to the outside environment by a waste exchanger fan.
Each main fan may be manually adjusted to operate at a variety of predetermined speeds via a fan switch. Each Peltier module can be manually adjusted to operate in various heating or cooling modes via a temperature switch. The electrical power to each Peltier is pulsed at a duty cycle corresponding to a particular heating or cooling mode of operation to optimize electrical efficiency. Each heat pump may be operated independently via separate fan and temperature switches, or may be operated simultaneously by a common fan and temperature switch. Alternatively, each heat pump may be operated automatically by the controller when the variable temperature seat is occupied by the activation of an occupant presence switch.
After an initial fan speed and Peltier temperature setting has been selected, the controller monitors the temperature information relayed from each heat pump. In addition, the controller may also be configured to monitor the ambient temperature of the air surrounding the variable temperature seat occupant as well as the temperature of the conditioned air directed to the variable temperature seat occupant, via the use of additional temperature sensors. The controller regulates the operation of each main exchanger fan, each waste exchanger fan, and each Peltier module according to a temperature climate control algorithm. The control algorithm is designed to maximize occupant comfort and minimize the possibility of equipment damage, occupant discomfort or even occupant injury in the event of a system malfunction.
The control algorithm is designed to interrupt or limit the power to the Peltier modules and/or each main exchanger fan in the event that the heat pump temperature exceeds a predetermined maximum temperature or a predetermined minimum temperature, indicating a possible heat pump malfunction. Additionally, the control algorithm is designed to interrupt power to the Peltier modules in the event that the temperature of the conditioned air directed to the variable temperature seat occupant exceeds a predetermined maximum or minimum temperature.
The control algorithm is also designed to limit the power to the Peltier modules during the cooling mode of operation when the temperature of the cooling air directed to the occupant exceeds a predetermined minimum cooling temperature and the temperature has not been adjusted for a predetermined period of time, thus minimizing possible occupant discomfort associated with overcooling the occupant""s back. In addition, the control algorithm is designed to limit the power to the Peltier modules during the cooling mode of operation when the temperature difference between the ambient air surrounding the variable temperature seat occupant and the conditioned air directed to the occupant is greater than a predetermined amount.